Influence of thermal treatment on the phase properties of HoNi2B2C

Effect of B and C concentration on crystallization and properties of HoNi2B2C

“…4d and f. However, in this case the correlation is more complex because the superconductivity again disappears if the level y = 0.03 is exceeded despite the similar lattice parameters V and c/a. According to Schmidt et al, plain superconductivity is observed for unit cell volumes V > 130.3Å 3 , non-superconducting properties for V < 130.15-130.20Å 3 and re-entrant behavior in the interval 130.3Å 3 > V > 130.2Å 3 [9,23]. The latter range is in fair agreement with the present finding.…”

Microscopic changes inHoNi2B2Cdue to thermal treatment and its effect on superconductivity

“…13,16 Not only chemical composition affects the physical properties of HoNi 2 B 2 C, also thermally activated processes have an important influence on the superconducting behavior of polycrystalline samples. 17,18 The degree of ordering introduced by thermal treatment at different temperatures in combination with subsequent quenching significantly changes the electronic properties of HoNi 2 B 2 C. The same phenomenon has been observed for borocarbide compounds with nonmagnetic rare earth ions. 18 So far, the microscopic origin of these changes, which depends on the frozen-in state of thermodynamic equilibrium, has not been resolved.…”

“…In order to have a reliable starting point for our investigations, we homogenized the as-cast samples for four weeks at 1100°C. 17,18 Then, the HoNi 2 B 2.1 C sample was cut into two pieces of equal size. Both pieces were annealed for two days, one at 800°C, the other at 1100°C.…”

Rare-earth metal transition metal borocarbide and nitridoborate superconductors

“…Additionally, a variable boron content in the range 1 < x < 2 was determined in a study aiming to clarify the phase equilibria in the system [58]. Furthermore, a clear dependence of the physical properties, that means transition temperatures, electrical resistivity, and magnetic order [107][108][109], on the annealing history of the sample was traced back to formation of vacancies and to some disorder of C and B up to a considerable level of 8.6 %, based on neutron powder diffraction using YNi 2 [ 10 B 2 C] [110]. At this point it has to be mentioned that 11 B and C are nearly indistinguishable both in X-ray and neutron diffraction and 10 B with a clearly different diffraction length in neutron scattering is highly absorbing complicating the situation.…”